Figure 7.

[Ca²⁺]_i responses to changing V_m during stimulation with ACh require extracellular Ca²⁺

A, simultaneous V _m (top) and F ₃₄₀/F ₃₈₀ (bottom) recordings during current injection (−5 to +5 nA; 20 s pulses at arrowheads) during 100 nm ACh in Ca²⁺‐free PSS. Note absence of sustained elevation (i.e. plateau phase) in [Ca²⁺]_i response. B, overlay of summary data for F ₃₄₀/F ₃₈₀ values at corresponding levels of V _m (binned according to level of current injection) during 100 nm ACh with 2 mm [Ca²⁺]_o and with Ca²⁺‐free PSS. Arrows indicate V _m and F ₃₄₀/F ₃₈₀ under respective conditions with zero current. Summary data are paired experiments for n = 8 endothelial tubes from 8 mice. *P < 0.05, F ₃₄₀/F ₃₈₀ during current injection versus F ₃₄₀/F ₃₈₀ with zero current.